1. Field of the Invention
This invention relates to a data transmission system, such as an optical submarine cable system, and node equipment and network management equipment used in the system.
2. Description of the Related Art
Information communication systems applied to a trunk network are required to be able to continue data transmission without the interruption of communication even when a failure has occurred. To meet the requirement, various methods for assuring the reliability of communication have been proposed. In large-scale networks, the configuration where a plurality of nodes are connected in a ring via a signal transmission line including a service line and a protection line has been widely used.
In this type of network, when no failure has occurred in the network, service traffic is held in the service line. When a failure has occurred in the service line, the transmission route of the service traffic is switched to the protection line. In this way, the service traffic is salvaged.
Furthermore, when there is no failure in the network, the protection line holds extra traffic or part-time traffic lower in priority than that of the service traffic. These traffics are cut off when a failure occurs.
Networks having such an architecture include systems complying with SDH (Synchronous Digital Hierarchy) and systems conforming to SONET (Synchronous Optical Network), an ANSI (American National Standards Institute) standard. The process related to the protection of service traffic is often realized by automatic distributed control using information exchange between pieces of node equipment. This type of function is called a self-healing function. The self-healing function in SDH is referred to as APS (Automatic Protection Switching). The details of APS have been written in, for example, ITU-T (Telecommunication Standardization Sector of ITU) Recommendation G. 841 distributed by the ITU (International Telecommunication Union).
With the recent rapid progress in IP (Internet Protocol) technology, a high-capacity, high-speed transmission of IP packets is becoming possible. In addition, the technique for detouring the transmission route of service traffic to an external network to salvage the service traffic is being realized. With this backdrop, the needs of communication operators have become diversified, which requires the network to have more flexibility in management than it has now.
As described above, with the recent advances in communication technology, the needs of communication operators have become diversified. This requires the network to have more flexibility in management than it has now.